The present invention relates to a wiper system for clearing a portion of a surface such as a windshield, and relates in particular to a mechanical drive for a large wiper.
The windshields or windows of large vehicles such as farming equipment, recreational vehicles, and buses are large and may be convex to provide a generous field of vision for their drivers. A windshield wiper system for these types of vehicles should be capable of clearing a large portion of a windshield for the driver. The windshield wiper systems on such vehicles should be capable of adequately sweeping dust, debris, rain and the like away from a significant portion of the windshield to allow the driver to see as well as possible through the windshield.
A typical windshield wiper system for a large window has a large wiper blade including a thin rubber edge. A windshield wiper drive system drives the wiper blade to sweep across and clear a portion of the windshield for the driver. Many windshield wiper drive systems contain a pantograph linkage that allows for the wiper blade to be kept in a steady orientation as it sweeps through an arc across the windshield.
In some previous pantograph arrangements an idler arm has controlled the blade angle, but the idler has had to be carried along by the wiper drive arm, and any looseness in such linkages causes lag and sloppiness in the movement of the wiper blade. As a result wiper blades often skitter ineffectively across a windshield.
At the point where the wiper blade has completed a sweep in one direction, it stops and changes direction. Many windshield wiper systems become wobbly or insecure when the wiper blade reaches the point at which it changes direction, resulting in a decrease in quality of the wiper blade's ability to sweep those portions of the windshield. Additionally, in many previous drive systems the reversal of the sweep at each end of the swept arc has required a significantly increased drive motor electric current.
In some previously available wiper drive systems pivot shafts for wiper drive arms have been asymmetrically located at one end of a drive mechanism housing, requiring careful consideration by a designer of a vehicle or machine with limited space for installation of such a wiper drive mechanism.
An improvement desired, then, is a wiper drive system capable of driving a large wiper blade on a large window, with continued control of the orientation of wiper blades and without requiring large increases in drive motor power at the ends of a swept arc.